CN1312460C - Device and method for measuring geometries of essentially two-dimensional objects - Google Patents

Abstract

The invention relates to a device and method for measuring geometries or structures of essentially two-dimensional objects (10) involving the use of an image processing sensory mechanism (14). According to the invention, the object to be measured is placed on an object supporting surface (12) and is measured on the side of the object supporting surface by means of an image processing sensory mechanism (14) that can be displaced underneath the object (10) in a plane running parallel to the object supporting surface (12).

Description

Apparatus and method for measuring geometric dimensions of substantially two-dimensional objects

technical field

The invention relates to a device for measuring the geometry or structure of an essentially two-dimensional object by means of an image processing sensor, wherein the object to be measured is placed on an object placement surface and image processing is provided on the object side Sensors, such as CCD cameras. Furthermore, the invention relates to a method for measuring the geometry or structure of an essentially two-dimensional object using an image processing sensor, wherein the object to be measured is placed on an object placement surface and on an object An image processing sensor, such as a CCD camera, is arranged on the side.

Background technique

For measuring the geometrical dimensions of primarily two-dimensional objects such as workpieces or tools, especially for obtaining quality features in testing technology, coordinate measuring devices with image processing sensors, such as CCD cameras, are preferably used. These measuring devices are generally set up in such a way that the object to be measured is illuminated from below, moved by means of a cross table and the structure of the object to be measured of interest is measured from above by means of an image processing sensor. A disadvantage of the construction principle is that the image processing sensor must be refocused for objects of different thicknesses. The secondary focusing, which is also necessary when the smallest height levels occur on the object, prolongs the measurement process.

Furthermore, in order to measure certain marks, the image processing sensor is usually positioned at the point of the mark, and then the contour of the workpiece is recorded and finally calculated. The entire overview of the measurement object is therefore not acquired.

In addition, the individual parts of the measurement object are approached several times in order to capture markers that are close to one another one after the other. This likewise prolongs the measurement time.

So-called scanning systems are also known in which a larger part of an area is scanned by means of strip sensors. A disadvantage of this system is that the image information is composed of a linear scanning movement in a first direction and sensor geometry in a second direction. This specialized geometry of the sensor also requires projection optics, which are largely incapable of precise imaging. The result is that measuring devices made according to this principle have only low precision.

Contents of the invention

The technical problem to be solved by the present invention is to further improve a device and a method of the above-mentioned type in such a way that two-dimensional objects or their geometric dimensions, especially object edges and object corners and object edges, can be measured very quickly with high measurement accuracy.

In order to solve this technical problem, it is mainly provided on the device side that the image processing sensor is arranged below the object and can be adjusted in a plane extending parallel to the surface on which the object is placed.

In particular, the moving image processing sensor is arranged in a closed housing which is closed on the object side by a transparent surface on which the object can be placed. It is of course also possible to place the object on a separate carrier at a distance from the transparent surface.

In a refinement, provision is made for an illumination means, preferably in the form of a luminous surface, to be arranged above the surface on which the object or workpiece is placed.

In particular, it is provided that the device comprises a housing with a closed base and a cover. The closed bottom contains the sensor with the optics and the drive mechanism, while on the cover side there is a transparent cover, such as a glass plate, on which the object to be measured can be positioned. The cover itself has lighting means, wherein measurements are only possible when the cover covers the lower part of the housing, ie is closed. The object is thus surrounded by the housing, ie the housing lower part and the cover plate, on all sides during the measurement, so that no inadvertent displacement of the object or other changes affecting the measurement can occur.

Furthermore, it can be provided that the object is surrounded in a focused manner by light sources, such as light-emitting diodes, which radiate in the direction of the object, so that the object is illuminated on the sensor side.

Telecentric objectives with a large depth of field can be used as projection optics for the image processing sensor. The depth of field can be, for example, 50 mm without limitation.

The position of the image processing sensor can be adjusted via an associated XY drive, wherein the position can be measured via a corresponding scale system.

An image memory can be connected to the image processing sensor, which represents the desired, in particular size, of the entire measurement area of the device. Furthermore, an evaluation calculation unit can be attached to the image memory of the measurement site, in particular of the entire measurement site, which performs a geometric calculation of the entire image content.

The image processing sensor preferably includes a matrix image processing sensor and is designed as a CCD matrix camera.

A method of the aforementioned type for measuring a substantially two-dimensional object, characterized in that the image processing sensor is arranged adjustably in a plane below the object placement surface, which plane extends parallel to the object placement surface .

The image processing sensor is therefore arranged displaceably in one plane below the measuring object with an upward viewing angle.

In this case, the image processing sensor can record images at several positions of the measurement site and combine these images computationally in the image memory to form a complete image. It is also possible to record images separately over the entire measurement site and to combine this image group to form a complete measurement image. The complete image can be evaluated geometrically by an image processing system. For example, the field of view of the sensor is 50×80 mm ² and the measurement site is 400×200 mm ² , which are just numerical values listed as examples.

The disadvantages inherent in the prior art can be reduced or avoided by the concept according to the invention. According to the invention, this is achieved in that the moving image processing sensor is arranged below the object, for example below a glass pane, with a view pointing towards the object, ie upward. This allows the object range to be measured, such as the edges of the measurement object, to lie in each case in the same plane, regardless of the thickness. Therefore no sensor focusing is required.

In addition, the use according to the invention of an optical system with a sufficient depth of field enables automatically graded measurements to be carried out partially in one position without focusing procedures being required.

In order to optimize the measurement time, according to the invention, the entire measurement site or parts of the measurement site are optionally scanned by aligning the positions of the image processing sensors relative to each other. This makes it possible to generate a complete image in the connected image processing computer. Measurement-technical calculations are performed in one pass over the entire image. The positioning process is thus omitted and a complete overview of the object to be measured is obtained.

The part of the measurement site itself can also be used as a partial complete measurement image, which is then calculated by an image processing system.

In particular, the precise positioning of the matrix-shaped image processing sensors avoids the disadvantages of the prior art.

Provision is preferably made to use an optical system with different working distances for measuring an object or a region of this object. In particular, however, an optical system can be used that has a zoom lens group that includes at least two lens groups that are each independently motor-displaceable in the axial direction. In this regard, reference is made to WO 99/53268, which is referred to in its disclosure.

In a preferred embodiment of the invention it is provided that the image processing sensor is first roughly aligned on the position of the object or object part to be measured, wherein during the alignment of the image processing sensor this image processing sensor travels with an acceleration a ₁ > 0 mm/s ² in order to then brake the image processing sensor and measure the position while the image processing sensor is moving with an acceleration a ₂ of 0 mm/s ² ≦a ₂ <a ₁ . If necessary, the object can be additionally supplied with a flash, or a CCD camera with a shutter can be used as an image processing sensor. The correlation between the movement of the sensor and the respective image to be captured is achieved by means of measures in which the image processing sensor is apparently stopped by means of a flash or a shutter, with the result that the measurement is carried out in spite of the fact that the image processing sensor may be at a position during the measurement. still.

Description of drawings

Further details, advantages and features of the invention can be derived not only from the claims, the features resulting therein on their own and/or in combination, but also from the following description of the preferred exemplary embodiment figures. The accompanying drawings show:

Figure 1. A schematic diagram of a device for measuring a two-dimensional object,

Fig. 2a+2b is a schematic diagram of a first embodiment of a measurement method,

Figures 3a+3b are schematic diagrams of a second embodiment of a measuring method.

Detailed ways

FIG. 1 shows purely in principle a device for measuring an essentially two-dimensional object 10 which is arranged on an object placement surface 12 . According to the invention, this mounting surface is transparent and in particular consists of a glass pane in order to be able to measure object 10 from below. An image processing sensor 14 is arranged adjustable in the X and Y directions of a coordinate measuring device below the object placement surface 12 . The image processing sensor preferably consists of a CCD matrix camera 16 , to which an optical system 18 , in particular in the form of a telecentric objective lens, with a large depth of field is connected.

The object mounting surface 12 can here be the surface of a housing in which the image processing sensor 14 can be adjusted relative to the object 10 in the X and Y directions. The housing surface is transparent here, with the object 10 either directly abutting against the housing surface or arranged equidistantly relative to the housing surface.

The moving image processing sensor 14 is arranged with a line of sight to the object 10 below the object 10 and below the object mounting surface 12, in particular formed of a glass plate, so that no focusing of the sensor 16 is required for a sufficient depth of field of the objective 18 , because the part of the object to be measured—such as the edge of the hole 20 in the exemplary embodiment—is located in the same plane regardless of the thickness of the object 10, that is, on the object placement surface 12 opposite the image processing sensor 14 Regardless of the position of the mounting surface, there is an equal distance.

If the object 10 is arranged directly on a glass pane in the present exemplary embodiment, it is of course also possible to arrange the object 10 at a distance from this glass pane, but equidistantly.

For illuminating the object, an illumination means, in particular in the form of a planar light strip 22 , is arranged above the object, ie on the side opposite the object 10 with reference to the image processing sensor 14 .

In this case, the planar bright wave band is to be integrated into a cover that closes the housing, in which the image processing sensor 14 with the optical system 18 and the drive mechanism is arranged, and the housing is passed through a transparent element on the side of the illumination field. , If the glass plate is closed, position the object to be measured on the glass plate. In this case, the measurement is generally only carried out when the cover plate with the bright band 22 completely covers the housing, ie closes off the glass pane side.

In order to carry out measurements accurately at high speed, it is provided according to the invention that the image processing sensor 14 takes images at a plurality of positions 24, 26, 28, 30, 32, 34, 36, 38 within the range of the object 10 to be measured, said positions In FIGS. 2 a and 3 a correspond essentially to the respective field of view 25, 37 of the image processing sensor 14 and are represented by a square framed by a dotted line, so that each image is then computationally assembled in the image memory into a corresponding The complete image in FIG. 2b or, for separately acquired images (FIG. 3a ), these are combined to form the complete measurement image in FIG. 3b. Geometric features, such as the position of the measuring point 44 , 46 or the distance 48 , 50 of the measuring point or measuring point, respectively, can then be calculated from the respective complete image 40 or 42 . The size of the fields of view 24 , 25 , 26 , 28 , 30 , 32 , 34 , 36 , 37 , 38 may be, for example, 50×80 mm ² , while the measurement site is 400×200 mm ² , but it is not limited thereto.

In other words, in order to optimize the measurement time, the entire measurement site ( FIG. 2 a ) or parts of the measurement site ( FIG. 3 a ) can optionally be scanned according to the invention by the positioning of mutually arranged image processing sensors such as matrix CCD cameras 16 . It is thus possible to generate a complete image 40 , 42 in the connected image processing calculator, wherein the measurement-technical calculations are carried out in one go over the entire image. The localization process is thus dispensed with and a complete overview of the object 10 to be measured is obtained. This measure avoids the disadvantages of the prior art due to the need for precise positioning of the matrix-shaped image processing sensors.

The measuring method can be optimized independently of this by first aligning the image processing sensor roughly at the position of the object to be measured, wherein the image processing sensor moves with an acceleration a ₁ >0 mm/s ² during the alignment of the image processing sensor , in order to then brake the image processing sensor and measure the position while the image processing sensor is moving with an acceleration a ₂ of 0 mm/s ² ≦a ₂ <a ₁ . An image processing sensor in the form of a CCD camera with a shutter can be used here, which has the advantage that an apparent stop of the sensor is achieved during the measurement regardless of sensor movement. The same functionality can be achieved with flash.

In other words, the image processing sensor is only roughly moved to the position to be measured, and then the measurement is made while the image processing sensor continues to move, but substantially without acceleration, the image processing sensor may be with v ₁ for example 50 to 200mm/s speed movement. The image memory required for the measurement can be identified in the image processing sensor by reaching the target site. Braking can thus be brought about by the image processing sensor by optically acquiring the object part containing the position.

The image processing sensor can be moved in such a way that the object or the measuring point or measuring point of the object is measured at a velocity v ₁ , and then the image processing sensor is accelerated rapidly, for example to a value of approximately 5000 to 15000 mm/s, so that then At an acceleration of 0 mm/s ² at a velocity v ₂ between 400 and 600 mm/s, the measuring point or measuring point is roughly aligned. The image processing sensor is then braked to a velocity v ₁ preferably between 50 and 150 mm/s for the measurement. During this time the object or the site to be measured can be flashed or the shutter of the image processing sensor can be opened and closed at the desired frequency. After the measurement has been completed, the image processing sensor is then accelerated in the above-mentioned sense in order to be aligned with a new measurement point or location.

Claims (28)

1. A coordinate measuring device for measuring the geometric size or structure of a two-dimensional object (10) by means of an illumination mechanism (22) and an image processing sensor (14), wherein the object to be measured is arranged on an object placement surface In (12), the lighting mechanism is arranged above the object placement surface, and the image processing sensor is arranged below the object placement surface, and the image processing sensor itself is positioned on the object placement surface in a plane parallel to the object placement surface. The X and Y directions of the coordinate measuring device can be adjusted, and it is characterized in that the image processing sensor (14) is only arranged below the object placement surface (12), and the lighting mechanism (22) arranged above the object placement surface constitutes a light-emitting surface . 2. Coordinate measuring device according to claim 1, characterized in that the image processing sensor (14) comprises a matrix image processing sensor. 3. Coordinate measuring device according to claim 1, characterized in that the image processing sensor is arranged in a closed housing which is transparent or see-through on the object side and forms the object placement surface (12) ; or the object placement surface extends parallel to the transparent or see-through surface of the housing. 4. Coordinate measuring device according to claim 1, characterized in that the lighting means (22) are integrated in a cover of the housing, wherein the cover closes the housing on the side of the object placement surface. 5. Coordinate measuring device according to claim 1, characterized in that a telecentric objective with a large depth of field is used as projection optics (18) of the image processing sensor (14). 6. Coordinate measuring device according to claim 5, characterized in that the projection optics (18) are surrounded by lighting elements for illuminating the surface of the object (10) on the side of the image processing sensor For lighting. 7. The coordinate measuring device according to claim 1, characterized in that, the position of the image processing sensor (14) can be adjusted by an X/Y drive mechanism subordinate to the sensor, and the position can be adjusted by a corresponding scale system to measure. 8. Coordinate measuring device according to claim 1, characterized in that an image memory is connected to the image processing sensor (14), which memory represents the desired size of the measurement site (40, 42). 9. Coordinate measuring device according to claim 7, characterized in that an evaluation unit is assigned to the image memory (40, 42) of the measurement point, which performs a geometric calculation of the entire image content. 10. The coordinate measuring device according to claim 2, characterized in that the matrix image processing sensor is a CCD matrix camera (16). 11. Coordinate measuring device according to claim 6, characterized in that the projection optical system is surrounded in focus by the illumination element. 12. The coordinate measuring device of claim 6, wherein the lighting elements are light emitting diodes. 13. The coordinate measuring device of claim 8, wherein the measurement site is the entire measurement site of the device. 14. A method for measuring the geometry or structure of a two-dimensional object (10) by means of a coordinate measuring device with an image processing sensor (14), wherein the object to be measured is arranged on an object placement surface (12), An illumination mechanism (22) is arranged above the object placement surface, and the image processing sensor is adjustablely arranged below the object placement surface in a plane extending parallel to the object placement surface, by means of the image processing The sensor measures the measurement site of the object, and is characterized in that, by means of image processing sensor (14) on a plurality of positions (24, 26, 28, 30, 32, 34, 36, 38) of the measurement site constituted in a matrix An image processing sensor (14) of the sensor is used to capture images and computationally assemble the images into a complete image (40, 42) in an image memory connected to the image processing sensor. 15. The method as claimed in claim 14, characterized in that an evaluation unit is assigned to the image memory of the desired or the entire measurement site, which performs a geometric calculation of the image content. 16. The method according to claim 14, characterized in that the images (24, 26, 28, 30, 32, 34, 36, 38) are taken separately over the entire measurement site and the image group is assembled into a complete image(40, 42). 17. The method as claimed in claim 16, characterized in that the complete image (40, 42) is calculated geometrically by an image processing system. 18. The method as claimed in claim 14, characterized in that the object (10) or a region of the object is measured with a moving image processing sensor (14). 19. method as claimed in claim 18 is characterized in that, for measuring object (10) or a position of this object, carry out following method step: - roughly aligning the image processing sensor (14) to the position of the object (10) to be measured, wherein this image processing sensor is ^moved with an acceleration a1 > 0 mm/s when aligning the image processing sensor, and - decelerating the image processing sensor in order to measure with an acceleration a 2 of 0 mm/s ² ≦ _{a 2} <a ₁ when the image processing sensor is in motion. 20. The method as claimed in claim 18, characterized in that the object (10) is flashed during the measurement, or a CCD camera with a shutter is used as image processing sensor (14). 21. The method according to claim 14, characterized in that a projection optics system with a variable working distance for measuring with the image processing sensor (14) is used, said projection optics system comprising at least two Lens groups that are independently motor movable in the axial direction. 22. The method as claimed in claim 14, characterized in that a planar bright wave strip is used as illumination means (22). 23. The method according to claim 14, characterized in that the image processing sensor (14) moves in the X and Y directions of the coordinate measuring device and is arranged in a fixed, closed housing, the housing Closed on the object side by a transparent surface on which the object (10) is placed or at a distance from the surface on a plane extending parallel to the surface, said transparent surface or plane is The object placement surface. 24. The method as claimed in claim 22, characterized in that the lighting means (22) are integrated in a cover, by means of which the housing is closed, wherein when the cover exposes the object placement surface (12) The measurement of the object (10) is interrupted. 25. The method as claimed in claim 14, characterized in that a telecentric objective with a large depth of field is used as projection optics (18) for the image processing sensor (14). 26. The method according to claim 14, characterized in that the position of the image processing sensor (14) can be adjusted by the X/Y drive mechanism of the coordinate measuring device, and the position can be measured by a corresponding scale system . 27. The method of claim 15, wherein the image content is the entire image content. 28. The method of claim 21, wherein the projection optical system is a projection optical system having a zoom lens set.

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